Preheater for grain dryer

ABSTRACT

A concurrent-countercurrent flow, grain dryer of the type having an enclosed bin with a wet grain inlet at the top and a dry grain outlet at the bottom includes means for introducing hot air as a drying medium for the grain in a flow concurrent with the grain. Means are also provided at the bottom of the bin to introduce cool air which flows countercurrent to the grain flow. First exhaust ducts are provided intermediate and transverse the hot and cool air ducts. A second preheat exhaust is formed in combination with each hot air inlet duct so that a certain amount of the hot inlet air will flow upwardly in a countercurrent direction to the downward flow of the grain to preheat the wet grain immediately after it enters the enclosed bin of the dryer.

United States Patent Fackler et a1.

Oct. 21, 1975 PREHEATER FOR GRAIN DRYER [73] Assignee: M & W GearCompany, Gibson City, 111,

[22] Filed: Sept. 11, 1974 [2]] Appl. No.: 504,997

[52] US. Cl. i. 34/170; 34/210; 98/55; 98/56 [51] Int. Cl. F26B 17/12[58] Field of Search 34/6 1,623. I68, 170, 174. 34/210, 2l2, 33. 224,225; 98/32, 33 A, 5256 [56] References Cited UNITED STATES PATENTS3,373,503 3/1968 Kline et a1. 34/170 3,710,449 1/1973 Rathbun 34/1703,727,323 4/1973 Meiners et a1. i i a 34/1 70 3,789,747 2/1974 Wassermanetal 98/32 Primary Examiner-John J. Camby Assistant Examiner-Henry C.Yuen Attorney, Agent, or FirmMolinare, Allegretti, Newitt & Witcoff 57ABSTRACT A concurrent-countercurrent flow, grain dryer of the typehaving an enclosed bin with a wet grain inlet at the top and a dry grainoutlet at the bottom includes means for introducing hot air as a dryingmedium for the grain in a flow concurrent with the grain. Means are alsoprovided at the bottom of the bin to introduce cool air which flowscountercurrent to the grain flow First exhaust ducts are providedintermediate and transverse the hot and cool air ducts. A second preheatexhaust is formed in combination with each hot air inlet duct so that acertain amount of the hot inlet air will flow upwardly in acountercurrent direction to the downward flow of the grain to preheatthe wet grain immediately after it enters the enclosed bin of the dryer.

5 Claims, 2 Drawing Figures U.S. Patent Oct. 21, 1975 PREHEATER FORGRAIN DRYER BACKGROUND OF THE INVENTION This invention relates to animprovement in a grain dryer and, more particularly, to the improvementof the preheater for a concurrent-countercurrent flow type grain dryerof the type disclosed in US. Pat. No. 3,727,323 issued Apr. 17, 1973 toElmo R. Meiners and John 0. Bradford.

Grain, particularly corn is now often dried before storing to preventwet pockets, mildew and consequent spoilage of the grain Fast, efficientdrying may be effected by the introduction of a generally heated, lowcontent drying medium (usually air) to the wet grain. The drying mediumis moved relative to the grain and accumulates moisture from the grain.The moisture saturated drying medium is then removed from contact withthe grain to provide grain having a relatively lower moisture content.

However, because the drying medium is usually heated to effect moisturetransfer, sudden transition in the temperature of the grain may resultor cause poor grain conditioning of the grain kernels. For example, thesudden transition of the grain from a relatively cool or ambienttemperature to the high temperature of the drying medium may cause thegrain to become scorched. That is, subjecting the cool grain to a hot(approximately 300F) blast of air will quickly evaporate moisture fromthe grain at and near the surface of the grain kernels. Simultaneously,very little moisture will transfer from the interior of the grainkernels to a position at or near the surface of the kernels. Consequently, the kernels lose the protection against scorching initiallyprovided by evaporative cooling of the moisture at or near the surfaceof the kernel.

Thus, prior art grain drying systems may cause scorching of the grainparticularly when the ambient temperature of the grain is very low.Typically, ambient grain temperatures are very low during the late fallin the Midwest when outdoor temperatures are well below freezing.

To avoid such problems, the grain could be heated slowly. However, sucha procedure would generally have to be done on a batch basis and wouldnot be as efficient as continuous drying systems. Also, batch dryingwould be more expensive. Thus, in order to be commercially appealing, animproved drying apparatus which avoids scorching problems should be acontinuous drying apparatus.

Concurrent-countercurrent grain dryers constitute a class of continuoustype grain dryers which are very efficient and which normally do notproduce an excess of cracked grain. Such dryers are continuous typedryers since grain continuously enters an inlet at the top of a dryingbin and flows downwardly past upper hot air ducts, intermediate exhaustducts. ower cool air ducts and out the bottom of the bin. The hot airflows concurrent with the grain to the intermediate exhaust duct. Coolair from the lower cool air ducts flows upwardly counter to the grainflow and exits at the same intermediate exhaust duct.

Although concurrent-countercurrent dryers are very effective,nevertheless when grain introduced at the top of the bin is especiallycold due to the ambient conditions external the dryer, scorching andgenerally poor grain conditioning is quite likely to occur. That is,when a great temperature or moisture differential exists between theambient condition grain and the drying medium, scorching will probablyoccur. Of course, scorching of the grain will undesirably reduce thevalue of the grain. Therefore, it is an object of this invention toprovide an improved concurrent-countercurrent grain dryer which providesa means for preheating the grain to thereby avoid scorching and toprovide better grain conditioning.

US. Pat. No. 3,727,323 refrered to above discloses a preheatingstructure for a grain dryer of the type similar to the presentinvention. The preheater in the reference patent is comprised ofseparate diamond shaped ducts positioned above and in alignment with hotair inlet ducts. The diamond cross section preheater ducts areperforated on all sides to receive a counterflow of hot air whichpreheats grain entering the bin. Additionally, the preheater ducts arevented at their opposite ends by adjustable shutters.

This specific preheater mechanism has proved to be very satisfactory andefficient. On the other hand, in stallation of such preheaters duringthe manufacturing process is a time consuming and burdensomeexpenditure, particulary in comparison with the improved structure ofthe present invention.

SUMMARY OF THE lNVENTlON In a principal aspect, the present inventioncomprises a grain dryer of the type having an enclosed bin with a wetgrain inlet and a dry grain outlet. A plurality of spaced horizontal hotfluid inlet ducts are provided for directing fluid drying mediumdownwardly through a continuously moving bed of grain. Below the hotfluid inlet ducts are a plurality of spaced horizontal cold fluid inletducts for directing a fluid cooling medium upwardly through the same bedof grain. The cold fluid inlet ducts are spaced from one another toprovide a plurality of grain discharges to the grain outlet. To providefor continuous downward grain bed movement or flow, means are providedfor adding wet grain through the wet grain inlet and means are alsoprovided for removing dry grain from the grain outlet. Intermediate thehot and cold fluid inlet ducts is a set of horizontal exhaust ductspositioned transverse the inlet ducts. The horizontal exhaust ductsexhaust the fluid from both the hot and cold fluid inlet ducts.

A manifold is provided at one end of the grain drying bin to supply hotfluid to the hot fluid inlet ducts and cold fluid to the cold fluidinlet ducts. The hot fluid inlet ducts are closed on three sides so thathot fluid may be discharged downwardly in a concurrent direction.

A perforated metal cap is positioned over the top of each hot fluidinlet duct. The cap is perforated metal so that hot fluid may beexhausted through the preheat exhaust duct formed by the perforatedmetal and the planar top of the hot fluid inlet duct. This upperpreexhaust duct thus receives and exhausts hot fluid flowing in adirection countercurrent to the grain flow. This countercurrent flow ofhot air preheats the downwardly flowing grain as it enters the bin andsubstantially prevents scorching of the grain during the dryingoperation.

It is thus an object of the present invention to provide an improvedgrain dryer having an improved preheater mechanism.

Another object of the present invention is to provide means in acountercurrent-concurrent type grain dryer for preheating the grain tothereby reduce or eliminate scorching, shattering of the wet grain andother deleterious effects which might occur by overheating or rap idlyheating the grain during the drying process.

It is a further object of the present invention to provide an improvedpreheater mechanism for a concurrent-countercurrent type grain dryerwherein the preheat mechanism is formed from the least number of partsand with a minimum amount of alteration to dryers that do not includeany preheat structure.

These and other objects, advantages and features of the presentinvention will be set forth in greater detail in the description whichfollows.

BRIEF DESCRIPTION OF THE DRAWING In the detailed description whichfollows, reference will be made to the drawing comprised of thefollowing two figures:

FIG. 1 is a cut-away perspective view of a typicalconcurrent-countercurrent flow, column type grain dryer incorporatingthe improved preheat exhaust structure of the present invention; and

FIG. 2 is a cross-sectional view of the grain dryer of FIG. 1illustrating the improvement of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The improved grain dryer of thepresent invention is substantially the same in construction as thatshown and disclosed in US. Pat. No. 3,727,323. However, the preheatexhaust construction shown in US. Pat. No. 3,727.3 23 has beeneliminated and the preheat exhaust construction of the present inventionhas been added.

Referring to the figures, the grain dryer of the present inventionincludes an enclosed bin comprised of opposed side walls and 12 endwalls 14 and 16, lower hopper walls 18 and 20 and upper roof panels 22and 24. Wet grain is conveyed to the interior of the bin formed by theserespective walls through a grain inlet 25 by means of an auger 26 toform a bed. The wet grain bed 28 fills the interior of the bin and flowsdownwardly by means of gravity.

Positioned along the bottom-portion of the bin to form a plurality ofspaced grain discharges are cold air inlet ducts 28. Each inlet duct 28is formed by a triangular cross section duct running the length of thebin. Ducts 28 are perforated on the two top triangular sides 29 and 31to permit discharge of cool fluid (air) in the upward direction.

The cold air inlet ducts 28 are separated from one another to definegrain discharge outlets 30. Metering rolls 32 control the rate of graindischarge through the outlets 30. A discharge auger 34 removes the driedor lower moisture content grain from the lower apex formed by the hopperwalls 18 and 20.

Positioned above and transverse to the cold air inlet ducts 28 arehorizontal perforated exhaust outlet ducts 36. The exhaust outlet ducts36 havera diamond shaped cross section and are formed of metal which areperfo rated on all four sides of the diamond to permit exhaust of coldair flowing countercurrent to the grain flow as well as hot air flowingconcurrent to the grain flow as explained below.

Positioned above and parallel to the cold air inlet ducts 28 are aplurality of horizontal hot air inlet ducts 38. Each hot air inlet duct38 has a U-shaped cross section with depending side walls 40 and 42 anda connecting top portion or crown 44. The hot air inlet duets 38 and inparticular the walls forming the ducts 38, walls 40, 42 and 44 are notperforated.

Hot air flowing into the hot air inlet ducts 38 is discharged downwardlyor in a concurrent direction with the flow of grain in the bin. Both thehot and cold air fed to the ducts 38 and 28, respectively, originate ina plenum chamber 46 adjacent one end of the ducts 38 and 28. The plenumchamber 46 is split into two portions whereby a single fan 48 isoperable to drive fluid directly into the cold air ducts 28 and througha heater 50 and hot air inlet 54 into the hot air ducts 38 to effect airmovement through the bed 28 of grain in the bin. The air movement andconstruction of this portion of the dryer is much like that shown inGraham U.S. Pat. No. 3,302,297.

The improvement of the present invention relates to the preheat exhaustducts 52 formed by the crown or top portion 44 and the perforated sidepanels 48 and 49 extending the length of the bin. The side panels 48 and49 are preferably formed from a single sheet of metal which is bent toform an inverted V shaped cap which fits over the duct 38.

As illustrated in FIG. I, the exhaust duct 52 formed by the side panels48, 50 and top portion or crown 44 is vented to the atmosphere at theend of the bin opposite the hot air inlets 54. Thus, a triangular shapedexhaust opening 56 is associated with each preheat exhaust duct 52. Anoptional adjustable shutter 58 may be positioned over opening 56 tocontrol the air flow rate from the preheat exhaust duct 52 to theatmosphere.

The acute angle of the sides 48 and 50 with top portion 44 is preferablysubstantially equal to the angle of repose of the grain being dried. Forexample, the angle of repose for wet corn is approximately 4245. Thus,the downward flow of grain is not impeded by this construction and thegrain will not collect and clog perfo rations 60 defined in the panels48 and 50.

In operation then, grain enters the top of the bin through grain inlet25 and is spread in the bin via action of auger 26 and flows downwardly.Hot air enters ducts 38 and flows downwardly in a concurrent directionas illustrated by the arrows in FIG. 2. A certain amount of the hot airflows upwardly along the sides 40 and 42 of the inlet ducts 38 andenters the perforations 60 of panels 48 and 50 forming the preheatexhaust duct 52. Thus, a certain amount of hot air preheats the wet cornor grain prior to primary heating by the downwardly directed flow of hotair from ducts 38.

The moisture laden hot air ultimately exhausts through exhaust ducts 36.Of course, as preveiously described, a portion of the hot air exhauststhrough the preexhaust ducts 52 to effectively preheat the grain. Thecountercurrent flow of cold air entering through ducts 28 also exhaustthrough the exahust ducts 36. Adjustment of the flow rate amount throughthe preexhaust ducts 52 is effected by operation of shutters 58.

In this manner, a countercurrent flow of hot air is provided to preheatespecially cold and wet grain. This slightly tempers the grain before itmoves into the concentrated area of the hot air inlet ducts. Thus, thetemperature differential between cold and wet grain and the hot fluid issmall initially and increases gradually as the grain flows downwardtoward the region of maximum hot air flow and entry. This avoidsscorching and sudden shock to the grain kernels resulting from theevaportion ofthe moisture at or near the surface of the kernel. ln thismanner, more efficient removal of moisture from the grain is effected.

lmportantly, the preheater arrangement of the present invention providesstructural advantages relative to the structure shown in U.S. Pat No.3,727,323. It is a structure of substantially increased simplicity. Thatis, the utilization of additional separate diamond shaped ducts is nolonger found necessary.

Finally, the structure of the present invention demonstrates improvedpreheating and grain drying results relative to the structure disclosedin US. Pat. No. 3,727,323. For example, the use of a preheat duct inassociation with each inlet duct provides improved preheat fluid flowthroughout the grain bed. The preheat arrangement of the presentinvention thus permits an increase in the temperature of the inlet ductair to 325F. from the former temperature of 300F. As a result, weestimate improved dryer efficiency of 40% to 50%.

Therefore, the subject matter of the present invention is to be limitedonly by the following claims and their equivalents.

What is claimed is:

1. In a portable continuous flow grain dryer of the type having anenclosed bin with a wet grain inlet at the top of said bin and a grainoutlet at the bottom of said bin, said bin including a plurality ofspaced parallel horizontal hot fluid inlet ducts for directing a fluiddrying medium downwardly through a bed of grain in said bin, a pluralityof spaced parallel horizontal cold fluid inlet ducts for directing afluid cooling medium upwardly through said bed of grain, said cold fluidinlet ducts positioned parallel to and below said hot fluid inlet ductsand spaced from one another to provide a plurality of grain dischargesto the grain outlet fluid inlet means at one end of said inlet ducts,means for adding wet grain through said wet grain inlet, means forwithdrawing dry grain from said grain outlet horizontal exhaust ductmeans intermediate said hot and cold fluid inlet ducts and perpendicularthereto to receive and exhaust fluid medium flowing from said hot inletducts in a concurrent direction to grain flow and also exhaust coldfluid medium flowing from said cold inlet ducts in a countercurrentdirection to said grain flow, each of said exhaust duct means havingoutlets through said bin on op posite sides thereof, and means forproviding hot fluid to said hot inlet ducts and cold fluid to said coldinlet ducts through said fluid inlet means at one end of said bin, theimprovement comprising:

preheat exhaust ducts positioned over each of said hot fluid inlet ductsand coextensive therewith, each preheat exhaust duct being formed inpart by a portion of a hot fluid inlet duct, each of said hot fluidinlet ducts including a substantially horizontal planar top anddownwardly depending sides. said preheat exhaust ducts each includingthe planar top of said hot fluid inlet duct to form the bottom portionthereof and a perforated panel over and closed on said planar top toform a longitudinal duct. said preheat exhaust ducts being ventedoutside said bin.

2. The improved structure of claim I wherein said preheat exhaust ductsare vented at the end of the bin opposite the one end of the bin forproviding hot fluid to the hot fluid inlet ducts.

3. The structure of claim 1 wherein said perforated panel is comprisedof first and second intersecting perforated panels forming alongitudinal duct of triangular cross section with said planar top.

4. The improved structure of claim 3 wherein said first and secondperforated panels each form an angle with said planar top substantiallyequal to the angle of respose of grain admitted to the bin.

5. The improved preheat ducts of claim 1 wherein each of said hot fluidinlet ducts is formed by a continuous single piece of material having aninverted U shaped cross section and said preheat exhaust duct iscomprised of a single perforated panel having an inverted Vcross-section forming a cap over the top of the

1. In a portable continuous flow grain dryer of the type having anenclosed bin with a wet grain inlet at the top of said bin and a grainoutlet at the bottom of said bin, said bin including a plurality ofspaced parallel horizontal hot fluid inlet ducts for directing a fluiddrying medium downwardly through a bed of grain in said bin, a pluralityof spaced parallel horizontal cold fluid inlet ducts for directing afluid cooling medium upwardly through said bed of grain, said cold fluidinlet ducts positioned parallel to and below said hot fluid inlet ductsand spaced from one another to provide a plurality of grain dischargesto the grain outlet fluid inlet means at one end of said inlet ducts,means for adding wet grain through said wet grain inlet, means forwithdrawing dry grain from said grain outlet horizontal exhaust ductmeans intermediate said hot and cold fluid inlet ducts and perpendicularthereto to receive and exhaust fluid medium flowing from said hot inletducts in a concurrent direction to grain flow and also exhaust coldfluid medium flowing from said cold inlet ducts in a countercurrentdirection to said grain flow, each of said exhaust duct means havingoutlets through said bin on opposite sides thereof, and means forproviding hot fluid to said hot inlet ducts and cold fluid to said coldinlet ducts through said fluid inlet means at one end of said bin, theimprovement comprising: preheat exhaust ducts positioned over each ofsaid hot fluid inlet ducts and coextensive therewith, each preheatexhaust duct being formed in part by a portion of a hot fluid inletduct, each of said hot fluid inlet ducts including a substantiallyhorizontal planar top and downwardly depending sides, said preheatexhaust ducts each including the planar top of said hot fluid inlet ductto form the bottom portion thereof and a perforated panel over andclosed on said planar top to form a longitudinal duct, said preheatexhaust ducts being vented outside said bin.
 2. The improved structureof claim 1 wherein said preheat exhaust ducts are vented at the end ofthe bin opposite the one end of the bin for providing hot fluid to thehot fluid inlet ducts.
 3. The structure of claim 1 wherein saidperforated panel is comprised of first and second intersectingperforated panels forming a longitudinal duct of triangular crosssection with said planar top.
 4. The improved structure of claim 3wherein said first and second perforated panels each form an angle withsaid planar top substantially equal to the angle of respose of grainadmitted to the bin.
 5. The improved preheat ducts of claim 1 whereineach of said hot fluid inlet ducts is formed by a continuous singlepiece of material having an inverted U-shaped cross section and saidpreheat exhaust duct is comprised of a single perforated panel having aninverted V cross-section forming a cap over the top of the hot fluidinlet duct.